The purpose of this project is to assess the safety & tolerability of daily oral doses of a calcimimetic agent, AMG 073, for 6 weeks in subjects w/primary hyperparathyroidism (HPT) and to assess the clinical effects of AMG 073 by evaluating changes in plasma intact PTH, total serum calcium, calcitonin, and bone specific alkaline phosphatase concentrations and urinary N-telopeptide/ creatinine ratios and characterize the pharmacokinetics of AMP 073 in subjects with HPT.